Notes for checking shift points in selector lever position "D" on a test trip - AH27.10-P-9407-01A

TRANSMISSION 722.5

The normal functions of the automatic transmission are checked on the basis of the test procedure described here.

The assessment of the operating principle and any transmission malfunctions inherently requires experience in handling automatic transmissions. If this is missing, it is practical to then draw on another automatic transmission of identical design, that is OK, for a comparison. If the test then reveals irregularities, then the reason for the detected faults can be discovered with the aid of "programmed repairs" or the diagnosis manual.

Before starting the test always check the oil level in the transmission, the idle speed of the engine, and the setting for the control pressure cable.

When testing, make sure that the transmission is not continuously shifted, particularly when under load. A great deal of heat is developed on the servo members during the shift operations. The following serve as a reference value:

Repeat any power shifting within a period of 15 seconds only once at the most.

Test drive

Use the test drive to determine whether all 5 gears have been shifted to.

Move vehicle up into highest gear
1. Selector lever position in position "4"
2. Accelerate vehicle to 90 km/h
3. Accelerator pedal in idle throttle position
4. Then shift immediately from position "4" to "D"
5. The 4th → 5th shift operation should then follow
6. Move selector lever from "D" → "4"= Downshift from 5th → 4th should then follow
7. Move selector lever from "4" → "3"= Downshift from 4th → 3rd should then follow
8. If two downshifts occur = All gears are then present
9. If, at "D" → "4" there is no downshift = A gear is missing.
Determine rpm ratio
1. 10. Speed = 100 km/h
2. 11. Check engine rpm in selector lever positions "3", "4" and "D"
  3rd gear = approx. 4500 rpm
  
  4th gear = approx. 3150 rpm
  
  5th gear = approx. 2300 rpm
  
  Determine missing gear through engine speed comparison.
During the test drive, not only the shift points must be checked, but also - primarily - the transitions during gear changes.
The upshifts at reduced throttle should be such that they are only perceptible when attention is paid to them. At full throttle and kickdown the gear changes is clearly perceptible, however the new gear must engage smoothly and the impression of powerful engine low-speed torque should be retained. For example, sudden engine revving up during an upshift gear change indicates the slipping of a power link (brake band or clutch) and therefore has to be examined more closely.

Automatic downshifts without accelerator are done at very low speeds and they are only perceivable with a great deal of attention (engine rpm increase). By contrast downshifts under kickdown along with an rpm increase are connected to a noticeable harsh engagement. In specific vehicle speed ranges a downshift with reduced or full throttle is possible.

Downshifts with the selector lever are either downshifts with the accelerator (e.g. on a hill) or transmission braking without the accelerator (e.g. on descents or when decelerating). Downshifts with the accelerator only need a few fractions of a second for the gear change, whereas transmission braking without the accelerator take between 1 and 2 seconds.

In drive mode "2" the 1 → 2 upshift occurs just before the engine's maximum speed.

All speed details are approx. values. They are valid for each standard valid rear axle ratio and tires. Deviations from the specified values, dependent on scatter at the transmission end, as well as in the speedometer display, are possible.

Vehicles with selection program: Shift position.

E = Economy

S = Standard

Note on shift points in selector lever position "2" and "3"

The upshift from 1-2 in drive mode "2" is only possible at maximum engine speed and the accelerator pedal at full throttle stop.

Shift points in selector lever position "2" and "3" are no longer given for reasons of simplification.